Rumors claim that Sherlock's brothers will appear in the fourth season of the hit TV series.

A lot of people are familiar with Mycroft Holmes who is claimed to be as smart and dysfunctional as the popular London detective. Mycroft is a character that has high deductive abilities that exceeds even that of his brother's. However, he does not want to exert physical effort to conclude cases. Moreover, it is claimed that he works for the British government.

Meanwhile, Sherlock has another brother named Sherrinford Holmes, who is the eldest among the Holmes brothers. According to documents, Sherlock Holmes belongs to a family of country squires where the eldest manages the household. If Mycroft has a job in the government, he cannot manage the house.

Rumors also say that an A-list actor will play the role of Sherrinford Holmes. Whispers add that the crew is planning to tap "Thor" and "Avengers" star Tom Hiddleston. In a Q&A in Brazil, "Sherlock" co-creator Mark Gatiss joked about casting Hiddleston for the role.

With the inclusion of Sherlock's brothers in the series, it is expected that the familial background of Sherlock will be revealed.

"Why are the Holmes brothers the way they are? What are their parents like? Maybe we'll see one day. I'd like to find a way of showing, more than we have, that [Mycroft] is actually even cleverer than Sherlock," Mark Gatiss said.

In addition, according to showrunner Steven Moffat, the characters of the TV series will be taken to another place. Moreover, the executive producer talked about a re-introduction that will lead to a darker climax, although he did not specify what this re-introduction will be. He assured that the crew behind the series has a lot of ideas for next season.

"Sherlock" season 4 is returning to BBC in early 2016 with no official date yet. However, the series will hold a Christmas special planned for December 2015 and will be based on the mystery "The Adventure of the Blue Carbuncle."